Production of copperized etched aluminum printing plates

ABSTRACT

Production of copperized deep-etched aluminum printing plates for use in offset printing by a procedure in which, after the aluminum plates are coated with a light-sensitive compound, exposed to light, developed, and etched, they are then copperized with a copperizing solution, the copperizing being effected by initially rubbing an essentially fresh copperizing solution at generally ambient temperature on said aforesaid treated aluminum plates, draining off and recovering excess copperizing solution, raising the temperature of a drained off and recovered copperizing solution to in the range of about 85*-95*F, and rubbing said initially copperized plate at least one or more times with such drained off and recovered heated copperizing solution until said plate has been copperized to the desired extent.

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tes tet [191 1 PRODUCTION OF COPPERIZED ETCIIED ALUMINUM PRINTING PLATES [75] Inventors: Lowell Koenig, Evanston; Albert Presco, Berkeley, both of I11.

[73] Assignee: Alden Press, llnc., Elk Grove Village, Ill.

[22] Filed: Feb. 9, 1973 [21] Appl. No.: 330,966

OTHER PUBLICATIONS Reed, R. F. Offset Platemaking Deep Etch, 3rd. Ed., 1963, LTF No. 504, Lithographic Technical [45] Dec. M], 1974 Primary ExaminerDavid Klein Attorney, Agent, or Firm-Wallenstein, Spangenberg,

Hattis & Strampel 7] STRACT Production of copperized deep-etched aluminum printing plates for use in offset printing by a procedure in which, after the aluminum plates are coated with a light-sensitive compound, exposed to light, developed, and etched, they are then copperized with a copperizing solution, the copperizing being effected by initially rubbing an essentially fresh copperizing solution at generally ambient temperature on said aforesaid treated aluminum plates, draining off and recovering excess copperizing solution, raising the temperature of a drained off and recovered copperizing solution to in the range of about 8595F, and rubbing said initially copperized plate at least one or more times with such drained off and recovered heated copperizing solution until said plate has been copperized to the desired extent.

10 Claims, 4 Drawing Figures PATENTEB DEC 1 DISH This invention is directed to significant improvements in the production of copperized, deep-etched aluminum printing plates for use in offset printing, particularly from the standpoint of achieving marked savings and economies and making a stronger and more durable printing image on the plate.

It has long been known, in offset printing operations, to utilize etched, so-called deep-etch, copperized aluminum printing plates. Such plates comprise photographic reproductions on metal of screened positive films. In use, they are wrapped around a printing press cylinder and they transfer an inked image via a blanket cylinder onto paper or other materials to be printed. Such printing plates are in appreciable commercial use. However, an even more extensive use thereof has been hampered by reason of the fact that the cost of producing such plates is relatively high. Our present invention makes possible the production of such plates in a far more economical manner than has heretofore been known and with marked savings in costs from a number of standpoints, all as is hereafter pointed out.

SUMMARY OF THE PRIOR ART Our invention will best be understood in relation to known, presently used procedures for making deepetch copperized aluminum printing plates. Typical or illustrative present practices, starting with a conventional grained aluminum plate, comprise the following steps:

Step 1. Plate is coated with a light-sensitive coating,

commonly a bichromate compound coating, usually ammonium bichromate.

Step 2. Plate is exposed to bright light to produce a positive image.

Step 3. Plate is developed manually or by machine with deep-etch chemical developing solution.

Step 4. Plate is etched with an aluminum etch solution.

Step 5. Plate is washed using alcohol or cellosolve type of solvent.

Step 6. Plate is copperized with a copperizing solution. The plate is placed on a flat surface normally on a so-called down-draft table. The fresh copperizing solution is poured from its container onto the plate and manually rubbed in by means ofa pad applicator over a period of time, commonly of the order of approximately a minute. The same procedure, namely, pouring of fresh copperizing solution onto the plate and manually rubbing it on the plate, is repeated at least twice and, more commonly, several times, usually from four to seven times per plate, depending upon the extent of copper deposition desired which, in turn, is related to the expected number of impressions or printed pieces to be made from the finished plate. Generally speaking, for each plate of a size of approximately 2 feet X 3 feet, each pour of fresh copperizing solution is approximately 8 fluid ounces and, therefore, the total copperizing solution consumption per plate is between about 32 and 56 fluid ounces. Based upon a selling price for conventional copperizing solutions in the range of $5 to $7 per gallon, the copperizing solution cost per 2 feet X 3 feet plate is approximately $l.50. In the foregoing procedure, a substantial proportion, commonly the major proportion, of the copperizing solution which is poured onto the plate, in the course of its application and its being rubbed onto the plate, passes into the drain line of the down-draft table and then is allowed to go to waste. This presents a potential pollution problem.

Step 7. Plate is washed with alcohol or a cellosolve type of solvent.

Step 8. Plate is lacquered, commonly with a liquid vinyl lacquer, which is manually buffed onto the plate and dried.

v Step9. Plate is inked using developing ink which is I manually buffed onto the plate.

Step 10. Plate is submerged in hot water; then the background coating is scrubbed off; then the plate is finished, and dried and gummed. The plate is then ready to be used in an offset printing press.

Variants or modifications of the foregoing procedure are known to the art but, in general, the foregoing out lined procedures are illustrative of certain commercial practices. The aforesaid platemaking procedures are usually carried out in airconditioned and/or temperatur-contr'olled rooms, the ambient temperatures therein commonly being about 68-72F.

BACKGROUND OF, THE PRESENT INVENTION .for use in the first copperizingstep, after the plates were processed through Steps l-5, or for the one or several additional copperizing steps after the initial copperizing step. This was attempted because of the fact that a substantial proportion, commonly the major proportion, of the copperizing solution which is poured onto the plate in the several applications of copperizing solution to the plate, each application being followed by rubbing the copperizing solution onto the plate by means of a pad, drains off and has conventionally been allowed to go to waste.

Such efforts were, however, unsatisfactory and unsuccessful. A chemical change, possibly an oxidative one, takes place in a relatively short time, after application to and rubbing on the plate, and more particularly during and after the excess copperizing solution is drained off from the down-draft table. When such previously used and drained off copperizing solutions are sought to be used for the initial copperizing of plates, or for the subsequent multiple copperizings of the plates, after the carrying out of Steps 1-5, inclusive, the adherence of the copper is poor and unsatisfactory. The result is that the finished copperized plates are, at best, capable of only short runs and the impressions are commonly useless. A generally similar situation obtains, as indicated above, when drained off copperizing solutions are sought to be used for application to a plate which had first previously been copperized with new or fresh copperizing solution.

SUMMARY OF THE PRESENT INVENTION We have made the surprising discovery that previously used drained off excess copperizing solution can be utilized very satisfactorily for the copperizing of aluminum printing plates under certain conditions. A primary condition is that said previously used drained off copperizing solution be heated to a temperature not substantially below 85F and below the flash point of the organic solvent component of the copperizing solution before it is applied to the plate. In addition, in the especially advantageous embodiments of our invention, such previously used drained off copperizing solution, so heated, is used for the subsequent copperizing applications to a given plate after the initial copperizing application has been made with fresh or new copperizing solution.

EMBODIMENTS OF THE PRESENT INVENTION In the practice of our invention, as noted above, it is particularly advantageous that the first or initial copperizing of the printing plate, after such preliminary procedures prior to the copperizing step have been carried out, be effected with fresh or new copperizing solution and this is most conveniently and best done at ambient temperatures which, as noted above, would be in the approximate range of 6872F. Then the additional application or applications of the copperizing solution, applied to the said first coating application, are of previously used or drained off copperizing solution which has been heated to a temperature not substantially below 85F. By so proceeding, excellent copper adherence is obtained and the plates function highly effectively and, in certain cases, better than if they were made using repeated or multiple applications of fresh or new copperizing solution on each plate as in the heretofore known prior copperizing practices as described above. For reasons pointed out below, it is especially desirable that the upper range of the temperature of heating be about 95F and, therefore, the following descriptions will be in terms of the use ofa heating temperature in the range of about 85-95F.

It has also been found, and it is within the broader scope of the novel teachings of our invention, to utilize for the application of the first or initial copper coating a previously used or drained off copperizing solution, or a mixture of minor proportions of fresh or new copperizing solution with previously used or drained off copperizing solution, provided that the previously used or copperizing solution has been heated to a temperature in the range of about 85-95F, and such copperizing solution is applied to the plate with the copperizing solution being at a temperature in the range of about Thus, for example, where (a) previously used or drained copperizing solution is'admixed with (b) fresh or new copperizing solution, for instance, in proportions of 70 to 95 parts by weight of (a) to 30 to 5 parts of (b), the (a) solution is first heated to a temperature within the range of about 8595F and then admixed with the (b) solution at ambient temperature; or, alternatively, the aforesaid mixtures of (a) and (b) can be heated to in the range of about 85-95F; and then said mixtures are applied, at a temperature in the range of about 8595F, to the plate to effect the copperizing. As noted above, such heated copperizing solutions can be used for the initial or first copperizing of the plate, as well as for the one or more copperizing applications to said plate. However, as also noted above, it is the especially important embodiment of our invention to use fresh or new copperizing solution for the first application of copperizing solution to a given plate and then to utilize, for the additional one or several copperizing applications, previously used or drained off copperizing solutions which have been previously heated to in the range of about 85-95F and which are applied at that temperature to the initially copperized plate. By so proceeding, after a buildup of previously used and recovered drained off copperized solution in the recovery tank to a desired volume, the copper concentration in the copperizing solution is maintained at a reasonably uniform level so that it is unnecessary to add fresh or new copper solution to the copperizing solution in the said recovery tank to maintain the copper concentration in the copperizing solution in the recovery tank at any particular level.

The practice of our invention also makes it possible,

' without adverse effect, to eliminate certain steps which were considered to be material in prior known procedures. This adds to the advantages of the practice of our invention. Viewed, however, from the standpoint alone of savings effect in consumption of copperizing solution, such savings have been approximately percent or, in other words, cost of copperizing solution per 2 feet X 3 feet plate has been about $0.30, employing teachings of our present invention, as against, as noted above, about $1.50 in the case of illustrative prior art procedures. Over and above the foregoing advantages of our invention, waste pollution is reduced since the drained off copperizing solution in heretofore commercially used procedures was discharged to waste whereas, in the practice of our invention, it is used over and over again so that, even if ultimately it is discharged to waste, only a very small percentage of what previously went to waste is so discharged.

An illustrative procedure utilizing teachings of our invention may be indicated as follows, whereby differences therebetween and the foregoing heretofore known illustrative procedure, referred to below for convenience as regular method, are delineated.

Step 1. Same as regular method.

Step 2. Same as regular method.

Step 3. Same as regular method.

Step 4. Same as regular method or can be eliminated if a developer etch combination is used in Step 3.

Step 5. Same as regular method or optionally can be eliminated.

Step 6. Plate is copperized with a copperizing solution as described below:

a. The plate is placed on a down-draft table.

b. One pour of fresh copperizing solution is applied to the plate and rubbed in for approximately 1 minute using a new or clean pad. The excess copperizing solution drains down into a recovery tank (approximately 90 percent recovery).

c. Recovered drained copperizing solution from (b) above, at a temperature in the range of about -95F, is pumped up from the recovery tank (apparatus effective for the carrying out of such copperizing solution is described below) for the additional or several repeated applications and rubbed on the plate, excess copperizing solution draining back to the recovery tank during and after each pour.

Step 7. Same as regular method.

Step 8. A non-drying ink containing some lacquer is applied to the plate and buffed down. This procedure is much faster than the regular Step 8 but the regular Step 8 can be used if desired.

Step 9. Same as regular method.

Step 10. Same as regular method (but faster if no lacquer option is used).

In the accompanying drawing there is disclosed, generally schematically, one form of apparatus which is effective in carrying out the copperizing steps of our present invention.

FIG. I shows the overall arrangement of the apparatus.

FIG. 2 shows the application from a hand-held bottle of fresh copperizing solution to a plate previously treated as described in Steps l5.

FIG. 3 shows the rubbing of the copperizing solution onto the plate by means of a hand-held rubbing and absorbent pad.

FIG. 4 shows a variant form of the apparatus in which the rubbing and absorbent pad is connected to a conduit leading from a tank containing previously used and recovered copperizing solution.

As shown in the drawing, a conventional down-draft table 11 comprises a frame 11 carried by support members l2 and connected to an exhaust fan 13 leading to a vent 14 to draw off air and fumes. A centrally positioned table-top 15, set within and spaced from the walls of the frame 11, on which table-top the printing plate 16 to be copperized is placed, is supported within said frame 11, by legs 17, above the bottom 18, said bottom being inclined or pitched to lead to a drain line 19 through which excess copperizing solution is removed from the printing plate in the rubbing operation. The excess copperizing solution passes by gravity from drain line 19 to a recovery tank 21. Disposed with said tank 21 is a submerged thermostatically controlled heater 22 to heat the drained and recovered copperizing solution 23 to a temperature within the range of about 85-95F and to maintain it within substantially that temperature range.

As will be clear in light of the foregoing disclosures, the printing plate 16, after carrying out the preliminary steps prior to copperizing, is placed flat on the tabletop 15. Then one pour of fresh copperizing solution, at ambient temperature, is poured onto the plate from hand-held bottle 24, or, alternatively, but less advantageously, previously used and drained off copperizing solution (admixed or not with minor proportions of fresh or new copperizing solution) in which said previously used and drained off copperizing solution has been heated to atemperature in the range of about 8595F, is poured onto the plate through line 26 leading from tank 22, and rubbed for a short period of time, commonly about a minute, more or less, using a new or clean pad 27, the excess copperizing solution draining off through drain line 19 into recovery tank 21. Drained, recovered copperizing solution, previously heated to a temperature in the range of about 85-95F in tank 21, is pumped by pump 25 (provided with control means for starting and stopping the pump) from said tank 21 through said line or discharge line 26, controlled by switch 28, for the repeated pours and rubbings with respect to the aforementioned initially copperized plate, excess copperizing solution being drained back into said recovery tank 21 for subsequent recirculation for reuse. An overflow pipe 29 is provided, connected to the tank 21.

In the use of the apparatus, drained recovered copperizing solution is first allowed to fill the tank 21 to a reasonably full level, controlled by the overflow pipe 29, before the said copperizing is begun to be used and recirculated, and the tank should desirably be kept reasonably full at all times.

In the FIG. 4 embodiment of apparatus useful in the practice of our invention, the discharge line 26 is shown connected to a rubbing pad 31 which may be impregnated with the copperizing solution and said impregnated pad may then be used to effect the subsequent copperizing steps after the initial copperizing with new or fresh copperizing solution, the valve means 28 serving manually to open and to shut off the supply of copperizing solution to the rubbing pad 31.

No novelty is claimed in the selection of lightsensitive coatings, developing solutions, aluminum etching solutions, copperizing solutions, ink compositions, and the like. Those can be used which are conventionally employed and which are known to the art for the production of etched or deep-etch aluminum printing plates. Thus, for instance, bichromates such as ammonium bichromate are most advantageously used as light-sensitive coatings, but it is also possible to utilize light-sensitive diazo compounds many of which are known and commerically available. Conventional developing solutions comprise aqueous solutions containing, for example, calcium chloride and zinc chloride and/or other salts, and acids such as, for instance, lactic acid. Deep etch solutions commonly comprise aqueous solutions containing calcium chloride and small proportions of ferric chloride and an acid such as hydrochloric acid. Copperizing solutions commonly contain a copper chloride, which may be cuprous chloride or cupric chloride or mixtures thereof, in an essentially non-aqueous organic solvent, commonly an alcoholic type of solvent, and containing an acid, for instance, hydrochloric acid. The flash point of the solvent is variable depending upon the particular organic solvent or solvents used in' the copperizing solution. Commercial copperizing solutions commonly use solvents which have flash points of about l00l 15F For reasons of safety considerations, the heating of the previously used or drained off copperizing solution should be at least 5-l0F below the flash point of the organic solvent or solvents present in the particular copperizing solution employed and, most advantageously, where the flash point is of the order of l00-l 15F, the upper temperature of heating of the previously used or drained off copperizing solution should not exceed about 95F. In at least most cases, it will also be found that, over and above and apart from flash point considerations, best results will occur where the previously used or drained off copperizing solution, as utilized in the practice of our invention, is applied at a temperature in the range of about 95F', and at times about 85-92F, to the plate.

What is claimed is:

1. In a method for making copperized, deep-etched aluminum printing plates for use in offset printing, wherein grained aluminum plates are coated with a light-sensitive compound, exposed to light, developed, etched, and copperized with a copperizing solution, the improvement which comprises effecting said copperizing by initially rubbing an essentially fresh copperizing solution at generally ambient temperature on said aforesaid treated aluminum plates, draining off and recovering excess copperizing solution, providing a previously used or drained off and recovered copperizing solution at a temperature in the range of not substantially below 85F but below the flash point of organic solvent present in said copperizing solution, and rubbing said initially copperized plate at least one or more times with such drained off and recovered heated copperizing solution until said plate has been copperized to the desired extent.

2. The method of claim 1, in which the temperature at which the drained off and recovered copperizing solution is applied to the plate is in the range of about 8595F.

3. The method of claim 1, in which the finally copperized plate, after washing with a solvent and dried, is

inked with a non-drying ink containing a lacquer.

4. The method of claim 3, in which final inking of said plate is effected with a developing ink, followed by removing the background coating of said plate by scrubbing with hot water, finishing, drying and gummmg.

5. In a method for making deep-etched copperized aluminum printing plates for use in offset printing, wherein grained aluminum plates are coated with a light-sensitive bichromate compound, exposed to light, developed, etched, and copperized with a copperizing solution, the improvement which comprises effecting said copperizing by initially rubbing an essentially fresh copperizing solution at generally ambient temperature on said aforesaid treated aluminum plates while supported on a down-draft table, draining off and recovering excess copperizing solution, raising the temperature to, or maintaining the temperature of, a drained off and recovered copperizing solution in the range of not substantially below 85F but below the flash point of organic solvent present in said copperizing solution, and rubbing said initially copperized plate at least one or more times with such drained off and recovered copperizing solution until said plate has been copperized to the desired extent.

6. The method of claim 5, in which the temperature at which the drained off and recovered copperizing solution is heated, or maintained, is in the range of about 85-95F.

7. In a method for making copperized, deep-etched aluminum printing plates for use in offset printing, wherein grained aluminum plates are coated with a light-sensitive compound, exposed to light, developed, etched, and copperized with a copperizing solution, the improvement which comprises providing a copperizing solution which, in at least major part, has previously been used for copperizing such plates, applying said copperizing solution, at a temperature not substantially below F but below the flash point of organic solvent present in said copperizing solution, as the initial application of copperizing solution to a given such plate and rubbing said copperizing solution onto said plate, draining off and recovering excess copperizing solution, raising or maintaining the temperature of drained off and recovered copperizing solution to in the range of not substantially below 85F but below the flash point of organic solvent present in said copperizing so lution, and rubbing said initially copperized plate at least one or more times with such drained off and recovered heated copperizing solution until said plate has been copperized to the desired extent.

8. The method of claim 7, in which the temperature to which the drained off and recovered copperizing solution is heated or at which it is maintained is in the range of about 85-95F.

9. ln a method for making deep-etched copperized aluminum printing plates for use in offset printing, wherein grained aluminum plates are coated with a light-sensitive bichromate compound, exposed to light, developed, etched, and copperized with a copperizing solution, the improvement which comprises providing a copperizing solution which, in at least major part, has previously been used for copperizing such plates, applying said copperizing solution, at a temperature not substantially below 85F but below the flash point of organic solvent present in said copperizing solution, as the initial application of copperizing solution to a given such plate and rubbing said copperizing solution onto said plate, draining off and recovering excess copperizing solution, raising or maintaining the temperature of drained off and recovered copperizing solution to in the range of not substantially below 85F but below the flash point or organic solvent present in said copperizing solution, and rubbing said initially copperized plate at least one or more times with such drained off and recovered heated copperizing solution until said plate has been copperized to the desired extent.

10. The method of claim 9, in which the temperature to which the drained off and recovered copperizing solution is heated or at which it is maintained is in the range of about 8595F. 

1. IN A METHOD FOR MAKING COPPERIZED, DEEP-ETCHED ALUMINUM PRINTING PLATES FOR USE IN OFFSET PRINTING, WHEREIN GRAINED ALUMINUM PLATES ARE COATED WITH A LIGHT-SENSITIVE COMPOUND, EXPOSED TO LIGHT, DEVELOPED, ETCHED, AND COPPERIZED WITH A COPPERIZING SOLUTION, THE IMPROVEMENT WHICH COMPRISES EFFECTING SAID COPPERIZING BY INTIALLY RUBBING AN ESSENTIALLY FRESH COPPERIZING SOLUTION AT GENERALLY AMBIENT TEMPERATURE ON SAID AFORESAID TREATED ALUMINUM PLATES, DRAINING OFF AND RECOVERING EXCESS COPPERIZING SOLUTION, PROVIDING A PREVIOUSLY USED OR DRAINED OFF AND RECOVERED COPPERIZING SOLUTION AT A TEMPERATURE IN THE RANGE OF NOT SUBSTANTIALLY BELOW 85*F BUT BELOW THE FLASH POINT OF ORGANIC SOLVENT PRESENT IN SAID COPPERIZING SOLUTION, AND RUBBING SAID INITIALLY COPPERIZED PLATE AT LEAST ONE OR MORE TIMES WITH SUCH DRAINED OFF AND RECOVERED HEATED COPPERIZING SOLUTION UNTIL SAID PLATE HAS BEEN COPPERIZED TO THE DESIRED EXTENT.
 2. The method of claim 1, in which the temperature at which the drained off and recovered copperizing solution is applied to the plate is in the range of about 85*-95*F.
 3. The method of claim 1, in which the finally copperized plate, after washing with a solvent and dried, is inked with a non-drying ink containing a lacquer.
 4. The method of claim 3, in which final inking of said plate is effected with a developing ink, followed by removing the background coating of said plate by scrubbing with hot water, finishing, drying and gumming.
 5. In a method for making deep-etched copperized aluminum printing plates for use in offset printing, wherein grained aluminum plates are coated with a light-sensitive bichromate compound, exposed to light, developed, etched, and copperized with a copperizing solution, the improvement which comprises effecting said copperizing by initially rubbing an essentially fresh copperizing solution at generally ambient temperature on said aforesaid treated aluminum plates while supported on a down-draft table, draining off and recovering excess copperizing solution, raising the temperature to, or maintaining the temperature of, a drained off and recovered copperizing solution in the range of not substantially below 85*F but below the flash point of organic solvent present in said copperizing solution, and rubbing said initially copperized plate at least one or more times with such drained off and recovered copperizing solution until said plate has been copperized to the desired extent.
 6. The method of claim 5, in which the temperature at which the drained off and recovered copperizing solution is heated, or maintained, is in the range of about 85*-95*F.
 7. In a method for making copperized, deep-etched aluminum printing plates for use in offset printing, wherein grained aluminum plates are coated with a light-sensitive compound, exposed to light, developed, etched, and copperized with a copperizing solution, the improvement which comprises providing a copperizing solution which, in at least major part, has previously been used for copperizing such plates, applying said copperizing solution, at a temperature not substantially below 85*F but below the flash point of organic solvent present in said copperizing solution, as the initial application of copperizing solution to a given such plate and rubbing said copperizing solution onto said plate, draining off and recovering excess copperizing solution, raising or maintaining the temperature of drained off and recovered copperizing solution to in the range of not substantially below 85*F but below the flash point of organic solvent present in said copperizing solution, and rubbing said initially copperized plate at least one or more times with such drained off and recovered heated copperizing solution until said plate has been copperized to the desired extent.
 8. The method of claim 7, in which the temperature to which the drained off and recovered copperizing solution is heated or at which it is maintained is in the range of about 85*-95*F.
 9. In a method for making deep-etched copperized aluminum printing plates for use in offset printing, wherein grained aluminum plates are coated with a light-sensitive bichromate compound, exposed to light, developed, etched, and copperized with a copperizing solution, the improvement which comprises providing a copperizing solution which, in at least major part, has previously been used for copperizing such plates, applying said copperizing solution, at a temperature not substantially below 85*F but below the flash point of organic solvent present in said copperizing solution, as the initial application of copperizing solution to a given such plate and rubbing said copperizing solution onto said plate, draining off and recovering excess copperizing solution, raising or maintaining the temperature of drained off and recovered copperizing solution to in the range of not substantially below 85*F but below the flash point or organic solvent present in said copperizing solution, and rubbing said initially copperized plate at least one or more times with such drained off and recovered heated copperizing solution until said plate has been copperized to the desired extent.
 10. The method of claim 9, in which the temperature to which the drained off and recovered copperizing solution is heated or at which it is maintained is in the range of about 85*-95*F. 